So I think I've found the root of all evil. Maybe my oplink is faulty, because if I power it from the usb port it works perfectly, but with an external power supply (through main or flexi port) it disconnects in every 2 minutes :/ (even if it's a stable 5.3V from a power supply)

I was wrong, my oplink control looses connection on 30m, I have set it up with ppm only and 100 tx power on both side..I'm using the antennas that was bunled with the fc. Both antennas are pointing up, is it possible that my oplink is dead? How can I test which side is dead?